Running SQL in Java and PHP

Size: px

Start display at page:

Download "Running SQL in Java and PHP"

Ellen Carr
5 years ago
Views:

1 Running SQL in Java and PHP FCDB Dr. Chris Mayfield Department of Computer Science James Madison University Feb 28, 2018

2 Introduction to JDBC JDBC = Java Database Connectivity 1. Connect to the database java.sql.connection 2. Send queries and updates java.sql.statement 3. Retrieve/process results java.sql.resultset import java. sql.* PostgreSQL s JDBC driver Download jar file from See Feb 28, 2018 Running SQL in Java and PHP 2 of 16

3 Load the driver Initialization during application startup: Class. forname (" org. postgresql. Driver "); ClassNotFoundException if driver not available Make sure the jar is in your class path Don t need to do this before every connection! Usually part of main method or static block Feb 28, 2018 Running SQL in Java and PHP 3 of 16

4 Connect to the DB Connection db = DriverManager. getconnection ( url, username, password ); URL format is specific to the DBMS jdbc:postgresql:database jdbc:postgresql://host/database jdbc:postgresql://host:port/database Internally, uses same library as psql and pgadmin Feb 28, 2018 Running SQL in Java and PHP 4 of 16

5 Execute a statement String sql = " SELECT * FROM mytab WHERE foo = 500 "; Statement st = db. createstatement (); ResultSet rs = st. executequery ( sql ); while (rs. next ()) { System. out. print (" Column 1 returned "); System. out. println (rs. getstring (1)); } rs. close (); st. close (); ResultSet can also do getint(i), getfloat(i),... Note that column indexes start at 1! For non-queries, use rs.executeupdate(sql) Feb 28, 2018 Running SQL in Java and PHP 5 of 16

6 Better yet, a prepared statement int foovalue = 500; String sql = " SELECT * FROM mytab WHERE foo =?"; PreparedStatement st = db. preparestatement ( sql ); st. setint (1, foovalue ); ResultSet rs = st. executequery (); while (rs. next ()) { System. out. print (" Column 1 returned "); System. out. println (rs. getstring (1)); } rs. close (); st. close (); The? syntax provides additional type safety String arguments are automatically escaped Helps prevent SQL injection attacks Feb 28, 2018 Running SQL in Java and PHP 6 of 16

7 Details about statements Use a single Statement instance as many times as you want However, only one ResultSet can exist per Statement or PreparedStatement at a given time If you need to run a query while processing a ResultSet, simply create and use another Statement If you are using threads, and several are using the database, you must use a separate Statement for each thread. When you are done using the Statement or PreparedStatement you should close it. Feb 28, 2018 Running SQL in Java and PHP 7 of 16

8 Details about result sets Before reading any values, you must call next() Returns true if there is a result More importantly, prepares the row for processing You should close a ResultSet once you have finished If you make another query with the RS s Statement then the ResultSet instance is closed automatically Now you try it! Create a Java application that outputs school divisions Feb 28, 2018 Running SQL in Java and PHP 8 of 16

9 Web Development 101 JSP and PHP by Example

10 Servlets and JSPs JSP = template for Java servlet See Servlet Goal: generate dynamic HTML response <html > <body > Hello! The time is now <%= new java. util. Date () % > <% // this block of code is called a scriptlet out. print ("<br > Your machine 's address is "); out. println ( request. getremotehost ()); %> </ body > </ html > Feb 28, 2018 Running SQL in Java and PHP 10 of 16

11 JSP example Database.java connects to DB Movie.java sample DB object index.jsp sample web form README how to compile/run HW5 Create a jsp/php application based on this example. Feb 28, 2018 Running SQL in Java and PHP 11 of 16

12 Introduction to PHP PHP stands for PHP Hyptertext Preprocessor acronym Scripting language for generating HTML pages <html > <body > Hello, today is <? php print ( Date ("l F d, Y" ));? >. </body > </html > Recommended tutorials: Feb 28, 2018 Running SQL in Java and PHP 12 of 16

13 Variables and strings Variables are untyped, need not be declared, start with $ $foo = 'bar '; $x = ' Step up to the $foo '; Single quotes = literal, double quotes = interpret $foo = " bar "; $x = " Step up to the $foo "; Concatenation is denoted by a dot $y = " $foo$ ". 'bar '; Feb 28, 2018 Running SQL in Java and PHP 13 of 16

14 Executing SQL in PHP Documentation: $dbconn = pg_ connect ( " host = localhost dbname =db user = foo password = bar ") or die ( ' Could not connect : '. pg_ last_ error ()); $query = ' SELECT * FROM authors '; $result = pg_ query ( $query ) or die ( 'Query failed : '. pg_last_error ()); //... PROCESS QUERY RESULTS HERE... pg_free_result ( $result ); pg_close ( $dbconn ); Feb 28, 2018 Running SQL in Java and PHP 14 of 16

15 Query results in PHP // generate an HTML table echo "<table >\n"; while ( $line = pg_ fetch_ array ( $result, null, PGSQL_ ASSOC )) { echo "\t<tr >\n"; foreach ( $line as $col_ value ) { echo "\t\t<td > $col_value </td >\n"; } echo "\t </tr >\n"; } echo " </ table >\n"; Feb 28, 2018 Running SQL in Java and PHP 15 of 16

16 PHP example Database.php connects to DB Movie.php sample DB object index.php sample web form README how to compile/run HW5 Create a jsp/php application based on this example. Feb 28, 2018 Running SQL in Java and PHP 16 of 16

Running SQL in Java and PHP

Running SQL in Java and PHP FCDB 9.6 9.7 Dr. Chris Mayfield Department of Computer Science James Madison University Mar 01, 2017 Introduction to JDBC JDBC = Java Database Connectivity 1. Connect to the